1. Field of the Invention
This invention relates to the preparation of polyamides by the anionic polymerization of lactams and is more particularly concerned with improvements in the polymerization process. 2. Description of the Prior Art
The anionic base-catalyzed polymerization of cyclic lactams to yield the corresponding polyamides is widely known and described in the literature. It has been reported that a wide variety of materials can be used as initiators or promoters of the polymerization. The use of acyl bislactams such as N,N'-terephthaloyl or N,N'-isophthaloyl biscaprolactam have long been known in this application (see U.S. Pat. No. 3,234,152) as well as certain N-substituted cyclic imides (see German Auslegeschrift No. 1294020).
We have now found that the use of a new class of promoter in the anionic polymerization of lactams gives rise to highly useful and different results from the above prior art promoters.